Help f5s scrambled

Hi
after watching sky movies for about 20 mims or so I get a scrambled sign come up and can't watch any further. If I switch box on / off issue is resolved. But I don't want to keep doing this.
box is connected via Ethernet on a home plug. It's a n line I'm running via mgcmd, is it cos I didn't set it up via ccmd?

any help appreciated